A Novel Hepadnavirus is Associated with Chronic Hepatitis and Hepatocellular Carcinoma in Cats

Conserved Functions of Orthohepadnavirus X Proteins to Inhibit Type-I Interferon Signaling

Orthohepadnavirus causes chronic hepatitis in a broad range of mammals, including primates, cats, woodchucks, and bats. Hepatitis B virus (HBV) X protein inhibits type-I interferon (IFN) signaling, thereby promoting HBV escape from the human innate immune system and establishing persistent infection. However, whether X proteins of Orthohepadnavirus viruses in other species display a similar inhibitory activity remains unknown. Here, we investigated the anti-IFN activity of 17 Orthohepadnavirus X proteins derived from various hosts. We observed conserved activity of Orthohepadnavirus X proteins in inhibiting TIR-domain-containing adaptor protein inducing IFN-β (TRIF)-mediated IFN-β signaling pathway through TRIF degradation. X proteins from domestic cat hepadnavirus (DCH), a novel member of Orthohepadnavirus, inhibited mitochondrial antiviral signaling protein (MAVS)-mediated IFNβ signaling pathway comparable with HBV X. These results indicate that inhibition of IFN signaling is conserved in Orthohepadnavirus X proteins.

Epidemiology of Pathogenic Retroviruses and Domestic Cat Hepadnavirus in Community and Client-Owned Cats in Hong Kong

Understanding the local epidemiology of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) in Hong Kong will inform retrovirus prevention strategies. Domestic cat hepadnavirus (DCH), a novel hepatitis-B-like virus, is commonly detected among client-owned cats in Hong Kong, but community cats have not been studied. The aims of this study were to investigate the frequency and potential risk factors for (i) FeLV and FIV among community and client-owned cats and (ii) perform molecular detection of DCH among community cats in Hong Kong. Blood samples from 713 cats were obtained from client-owned (n = 415, residual diagnostic) and community cats (n = 298, at trap-neuter-return). Point-of-care (POC) testing for FeLV antigen and feline immunodeficiency virus (FIV) anti-p15 and p24 antibodies was performed. FeLV-positive samples were progressed to p27 sandwich enzyme-linked immunosorbent assay. Whole blood DNA was tested with qPCRs for FeLV U3 and gag, and nested PCRs where additional information was required. DCH qPCR was performed on a subset of community cats (n = 193). A single, regressive, FeLV infection was detected in a client-owned cat (1/415 FeLV U3 qPCR positive, 0.2%, 95% CI 0.0-1.3%). Five/415 client-owned cats tested presumably false FeLV-antigen positive (qPCR negative). No markers of FeLV infection were detected in community cats (0/298; 0%). FIV seroprevalence was much higher in community cats (46/298, 15.4%) than in client-owned cats (13/415, 3.1%) (p < 0.001). Mixed breed was a risk factor for FIV infection in client-owned cats. Neither sex nor age were associated with FIV infection. DCH DNA was detected in 34/193 (17.6%) community cats (median viral load 6.32 × 103 copies/reaction). FeLV infection is rare in Hong Kong, negatively impacting the positive predictive value of diagnostic tests. FeLV-antigen testing remains the screening test of choice, but confirmation of a positive result using FeLV qPCR is essential. FIV infection is common in community cats and the absence of a sex predisposition, seen previously in cats managed similarly, raises questions about virus-transmission dynamics in these groups. DCH infection is very common in Hong Kong, both in client-owned and community cats, highlighting the importance of understanding the pathogenic potential of this virus for cats.

Domestic Cat Hepadnavirus Antigens in Lymphoma Tissues. Comment on Beatty et al. Domestic Cat Hepadnavirus and Lymphoma. Viruses 2023, 15, 2294

We are addressing the comments made by Beatty et al [...].

Domestic cat hepadnavirus detection in blood and tissue samples of cats with lymphoma

Domestic cat hepadnavirus (DCH), a relative hepatitis B virus (HBV) in human, has been recently identified in cats; however, association of DCH infection with lymphoma in cats is not investigated. To determine the association between DCH infection and feline lymphoma, seven hundred and seventeen cats included 131 cats with lymphoma (68 blood and 63 tumor samples) and 586 (526 blood and 60 lymph node samples) cats without lymphoma. DCH DNA was investigated in blood and formalin-fixed paraffin-embedded (FFPE) tissues by quantitative polymerase chain reaction (qPCR). The FFPE lymphoma tissues were immunohistochemically subtyped, and the localization of DCH in lymphoma sections was investigated using in situ hybridization (ISH). Feline retroviral infection was investigated in the DCH-positive cases. DCH DNA was detected in 16.18% (11/68) (p = 0.002; odds ratio [OR], 5.15; 95% confidence interval [CI], 2.33-11.36) of blood and 9.52% (6/63) (p = 0.028; OR, 13.68; 95% CI, 0.75-248.36) of neoplastic samples obtained from lymphoma cats, whereas only 3.61% (19/526) of blood obtained from non-lymphoma cats was positive for DCH detection. Within the DCH-positive lymphoma, in 3/6 cats, feline leukemia virus was co-detected, and in 6/6 were B-cell lymphoma (p > 0.9; OR, 1.93; 95% CI, 0.09-37.89) and were multicentric form (p = 0.008; OR, 1.327; 95% CI, 0.06-31.18). DCH was found in the CD79-positive pleomorphic cells. Cats with lymphoma were more likely to be positive for DCH than cats without lymphoma, and infection associated with lymphoma development needs further investigations.

Hepadnavirus Infection in a Cat with Chronic Liver Disease: A Multi-Disciplinary Diagnostic Approach

A 3-year-old female stray, shorthair cat, with clinical signs and serum chemistry markers indicative of hepatic disease, was diagnosed with domestic cat hepadnavirus (DCH) infection. Coupling molecular and serological data, the infection was seemingly contextualized into a chronic phase, since IgM anti-core antibodies, a marker of early-stage Hepatitis B Virus (HBV) infection, were not detected. However, the cat possessed IgG anti-core, a common indicator of chronic HBV infection in human patients and did not show seroconversion to the anti-DCH surface antigen, considered protective during HBV infection and associated with long-term protective immunity. On genome sequencing, the DCH strain showed 98.3% nucleotide identity to strains previously identified in Italy.

Genetic Diversity of Domestic Cat Hepadnavirus in Southern Taiwan

Domestic cat hepadnavirus (DCH) is an infectious disease associated with chronic hepatitis in cats, which suggests a similarity with hepatitis B virus infections in humans. Since its first identification in Australia in 2018, DCH has been reported in several countries with varying prevalence rates, but its presence in Taiwan has yet to be investigated. In this study, we aimed to identify the presence and genetic diversity of DCH infections in Taiwan. Among the 71 samples tested, eight (11.27%) were positive for DCH. Of these positive cases, three cats had elevated levels of alanine transaminase (ALT) and aspartate transaminase (AST), suggesting an association between DCH infection and chronic hepatitis. Four DCH-positive samples were also tested for feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) coinfection. One sample (25%) was positive for FIV, whereas there was no positive sample for FeLV (0%). In addition, we performed whole genome sequencing on six samples to determine the viral genome sequences. Phylogenetic analyses identified a distinct lineage compared with previously reported sequences. This study highlights the importance of continuous surveillance of DCH and further research to elucidate the pathophysiology and transmission route of DCH.

Quantification of domestic cat hepadnavirus DNA in various body fluid specimens of cats: the potential viral shedding routes

Domestic cat hepadnavirus (DCH) belongs to the Hepadnaviridae family together with human hepatitis B virus (HBV) that remains to be a major health problem worldwide. The transmission of HBV infectious virion has been one of the essential factors that contribute to high number of HBV infection in humans. It has been long known that various body fluid specimens of human with chronic HBV infection contain HBV DNA and demonstrated to be infectious. In contrast to this knowledge, the detection of DCH in various body fluid specimens of cats, has not been reported. This study explored the detection of DCH DNA in various body fluid specimens of cats by quantitative polymerase chain reaction (qPCR) and investigated whether the detection of DCH DNA from broader routes was correlated with any genomic diversity by phylogenetic analysis. A total of 1,209 body fluid specimens were included, and DCH DNA was detected not only in 4.70% (25/532) of blood samples; but also in 12.5% (1/8), 1.14% (1/88), 2.54% (10/394), and 1.65% (3/182) of auricular swab (AS), nasal swab (NS), oral swab (OS), and rectal swab (RS) specimens, respectively. Furthermore, the level of DCH DNA detected in the blood was significantly correlated with DCH DNA detection in OS (P = 0.02) and RS (P = 0.04) specimens. Genomic analysis revealed that there was no notable genomic diversity within the complete genome sequences obtained in this study. In conclusion, this study highlighted the presence of DCH DNA in various body fluid specimens of cats, and the potential role of these specimens in DCH horizontal transmission within the cat population warrants further studies.

The detection and full genomic characterization of domestic cat Orthohepadnaviruses from Türkiye

BACKGROUND

Domestic cat hepadnaviruses (DCHs) have been described as a novel virus that can infect cats.

OBJECTIVE

The aim of our study is the first identification and molecular characterizations of DCH infection in Turkish domestic cats.

METHODS

The blood, organ and ascites fluid samples from 550 cats were randomly sampled. The presence of DCH nucleic acid was investigated by using both in the literature and newly designed primers.

RESULTS

It was found that the hepadnavirus positivity rate is 4% (22/550) in Türkiye. The full genomic characterization was performed on 13 of 22 samples, and others were characterized as nearly full genome. In this study, we highlight that whole blood samples should be also screened for DCH, not only serum samples as has frequently been done in other studies. DCH-infected cats were also found positive (54.54%, 12/22) for Feline leukaemia virus infection. BLAST results revealed that Turkish DCHs have 86.32%-99.08% homology with strains in the GenBank database, enabling us to construct phylogenetic trees.

CONCLUSIONS

According to this study's results, it is suggested that this infection should be added to veterinary diagnostic panels worldwide. Additionally, we suggest that our new synthesized primers for the amplification of X gene can also be used for diagnosis.

Detection and genetic characterization of domestic cat hepadnavirus in cats with cavitary effusions

After the identification of the novel domestic cat hepadnavirus (DCH) in 2018, its potential pathogenetic role in feline hepatic diseases has been suggested. Following the detection of DCH in a cat's serum and peritoneal effusion, the aim of this study was to retrospectively investigate the presence of DCH in cats with and without cavitary effusions along with DCH presence in effusions. Stored serum and effusion samples from cats with and without effusions admitted to the Veterinary Teaching Hospital of Lodi (Italy) in 2020-2022 were included based on results of hematobiochemical parameters. Effusions were classified based on cytological and physicochemical findings. The likelihood of liver damage was estimated based on clinical and laboratory findings. Samples were tested for DCH presence by quantitative PCR (qPCR). Positive samples were subjected to whole genome sequencing and phylogenetic analysis. DCH was detected in both serum and peritoneal effusion samples of 2/72 (2.8%) enrolled cats, included in the group with effusions (2/33; 6.1%), with one cat showing inflammatory and the other non-inflammatory effusion. Both DCH-positive cats belonged to the group with a likelihood of liver damage (2/22, 9.1%). Phylogeny showed that the DCH sequences from this study clustered with the prototypic Australian strain but were not included in the clade with other Italian DCH sequences. Results suggest the circulation of different DCH variants in Italy and show the presence of DCH in effusion samples from DCH-positive cats, mirroring the presence of HBV in body fluids from HBV-infected humans. Further studies are still recommended to define the pathogenic role of DCH in cats.

Non-hormonal Clitoromegaly due to Clitoral Priapism Caused by Appendicitis/Appendectomy

Clitoromegaly usually develops due to hyperandrogenism. There are a few cases of clitoromegaly described without clinical and biochemical hyperandrogenism. Clitoromegaly due to clitoral priapism and clitoral priapism after appendectomy have not been reported previously. A 7-year-old girl was referred for enlargement of the clitoris. She reported having a mild, pulsating clitoral pain starting three days after an appendectomy operation. Subsequently, painful swelling and an increase in the size of the clitoris was observed. Her growth and physical examination were otherwise normal. Causes of the clitoromegaly due to androgen excess were excluded after a comprehensive work-up. Color Doppler ultrasound revealed a high peak systolic velocity and resistance in the cavernosal artery, consistent with clitoral priapism. The clitoromegaly and associated symptoms improved significantly with oral pseudoephedrine and intracavernosal aspiration. This unique case illustrates that clitoral priapism is a rare, non-hormonal cause of clitoromegaly and may occur after appendectomy. Pseudoephedrine treatment is helpful in alleviating the symptoms.

Exploring the link between viruses and cancer in companion animals: a comprehensive and comparative analysis

Currently, it is estimated that 15% of human neoplasms globally are caused by infectious agents, with new evidence emerging continuously. Multiple agents have been implicated in various forms of neoplasia, with viruses as the most frequent. In recent years, investigation on viral mechanisms underlying tumoral transformation in cancer development and progression are in the spotlight, both in human and veterinary oncology. Oncogenic viruses in veterinary medicine are of primary importance not only as original pathogens of pets, but also in the view of pets as models of human malignancies. Hence, this work will provide an overview of the main oncogenic viruses of companion animals, with brief notes of comparative medicine.

Serological and Molecular Survey on Domestic Dog Hepadnavirus in Household Dogs, Italy

The discovery of hepadnaviruses in cats (domestic cat hepadnavirus, DCH) and of a DCH-like virus in dogs has raised several questions regarding the role of these viruses in pets, with particular emphasis on their potential impact on animal health and epidemiology, as well as possible zoonotic implications. In this study, by screening an age-stratified collection of 600 canine serum samples for DCH with an ELISA assay based on the recombinant core antigen (DCHCAg), specific antibodies were found with an overall prevalence of 10.0% (60/600), with a higher prevalence in younger and older dogs. By retesting the canine DCHCAbs-positive sera with an ELISA test based on the recombinant surface protein of DCH (DCHSAg), a total of 18 sera (30%, 18/60) also contained IgG anti-DCHSAg. All the sera were also assessed molecularly using either a consensus hepadnavirus PCR or a specific real-time PCR for DCH. Hepadnavirus DNA was detected in four seronegative dogs, with a prevalence rate of 0.7% (4/600). On sequence analysis of the polymerase region amplified with pan-hepadnavirus primers, the amplicons displayed the highest nucleotide identity (97.3-99.6%) to DCH sequences detected in cats and to the domestic dog hepadnavirus recently identified in a canine serum sample from Italy.

Domestic Cat Hepadnavirus: Molecular Epidemiology and Phylogeny in Cats in Hong Kong

Domestic cat hepadnavirus (DCH) is an emerging virus related to the hepatitis B virus (HBV). The pathogenic potential of DCH in cats remains to be established. The molecular prevalence of DCH varies widely in the regions investigated so far. The aim of this study was to determine the prevalence, load, and risk factors for DCH detection among cats in Hong Kong, and to generate molecular and epidemiological data on the DCH strains circulating in cats in Hong Kong. DCH DNA was detected using DCH-specific qPCR in 57/513 (11.1%) residual diagnostic blood samples from owned cats. The median viral load was 8.85 × 103 copies/mL of whole blood (range for the 5th to the 95th percentile, 3.33 × 103 to 2.2 × 105 copies per mL). Two outliers had higher viral loads of 1.88 × 107 copies/mL and 4.90 × 109 copies/mL. DCH was detected in cats from 3 months to 19 years of age. Sex, age, neuter status, breed, or elevated serum alanine aminotransferase were not statistically associated with DCH DNA detection. On phylogenetic analysis based on 12 complete genome sequences, the Hong Kong DCH viruses clustered in Genotype A with viruses from Australia and Asia (clade A1), distinct from viruses from Europe (clade A2). Sequence analysis found that DCH has similar epsilon and direct repeat regions to human HBV, suggesting a conserved method of replication. Based on our findings, the DCH strains circulating in Hong Kong are a continuum of the Asiatic strains.

Prevalence and Genomic Sequence Analysis of Domestic Cat Hepadnavirus in the United States

Hepadnaviruses are partially double-stranded DNA viruses that infect a variety of species. The prototypical virus in this family is the human hepatitis B virus, which chronically infects approximately 400 million people worldwide and is a risk factor for progressive liver disease and liver cancer. The first hepadnavirus isolated from carnivores was a domestic cat hepadnavirus (DCH), initially identified in Australia and subsequently detected in cats in Europe and Asia. As with all characterized hepadnaviruses so far, DCH infection has been associated with hepatic disease in its host. Prevalence of this infection in the United States has not been explored broadly. Thus, we utilized conventional and quantitative PCR to screen several populations of domestic cats to estimate DCH prevalence in the United States. We detected DCH DNA in 1 out of 496 animals (0.2%) in the U.S. cohort. In contrast, we detected circulating DCH DNA in 7 positive animals from a cohort of 67 domestic cats from Australia (10.4%), consistent with previous studies. The complete consensus genome of the U.S. DCH isolate was sequenced by Sanger sequencing with overlapping PCR products. An in-frame deletion of 157 bp was identified in the N-terminus of the core open reading frame. The deletion begins at the direct repeat 1 sequence (i.e., the 5′ end of the expected double-stranded linear DNA form), consistent with covalently closed circular DNA resultant from illegitimate recombination described in other hepadnaviruses. Comparative genome sequence analysis indicated that the closest described relatives of the U.S. DCH isolate are those previously isolated in Italy. Motif analysis supports DCH using NTCP as an entry receptor, similar to human HBV. Our work indicates that chronic DCH prevalence in the U.S. is likely low compared to other countries.

Comparative Oncology: Management of Hepatic Neoplasia in Humans and Dogs

Primary hepatic neoplasia is uncommonly reported in dogs. Hepatocellular carcinoma (HCC) is the most frequent neoplasia identified in dogs and considerable effort has been committed towards identifying definitive and palliative treatment options. HCC is well recognized in humans as a sequelae of liver disease such as hepatitis or cirrhosis, while in dogs a similar link has failed to be fully elucidated. Management of HCC in people may be curative or palliative dependent on staging and transplant eligibility. Despite differences in etiology, there is substantial similarity between treatment options for liver neoplasia in human and veterinary medicine. The below summary provides a comparative discussion regarding hepatic neoplasia in dogs and people with a specific focus on HCC. Diagnosis as well as descriptions of the myriad treatment options will be reviewed.

Infectious Causes of Neoplasia in the Domestic Cat

Simple Summary

Increasingly, cancers are being linked to infections with viruses, bacteria, and parasites in human medicine. This review summarises the current literature regarding neoplasia occurring in association with infectious diseases in domestic cats. To date, most studies have focused on the role of viruses, especially feline leukaemia virus and feline immunodeficiency virus in association with lymphoma, or the role of papillomavirus in cutaneous and oral neoplasms in cats. Recently, there has been a focus on a potential role of mouse mammary tumour virus in feline mammary carcinoma and lymphoma and studies assessing the potential role of gammaherpes virus and hepadnaviruses in feline neoplasia. Additionally, there has been some focus on potential bacterial and parasitic associations with neoplasia; including reports assessing potential associations between Helicobacter species and gastrointestinal neoplasms, and case reports of neoplasia in association with Platynosomum fastosum and Opisthorchis viverrini.

Abstract

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

Domestic cat hepadnavirus associated with hepatopathy in cats: A retrospective study

Background

Whether domestic cat hepadnavirus (DCH) infection is associated with clinical disease remains to be determined.

Objectives

To determine the relationship between DCH detection, hematology, serum bichemistry and liver histology in DCH‐positive cats.

Animals

One thousand twenty‐two cats in Thailand without concurrent diseases and not undergoing treatments adversely affecting the liver.

Methods

Retrospective cross‐sectional study. Samples derived from cats with concurrent virus detection were excluded. DCH detection was determined in blood and fresh‐frozen liver by quantitative polymerase chain reaction (qPCR) and further investigated in liver sections showing histological parenchymal disorders (HPD) and normal liver (HNL) using in situ hybridization (ISH). Proliferative/apoptotic activities were determined using immunohistochemistry and ISH panels. Biochemical variables and risk factors for DCH infection were investigated.

Results

Six hundred sixty‐one (557 blood and 119 liver samples) cats were included. DCH was detected in 18.50% (103/557), 13.85% (9/65), and 3.70% (2/54) of the blood, HPD, and HNL groups, respectively. Cats with DCH revealed abnormally high activity of aspartate aminotransferase (AST) (P = .001) and alanine aminotransferase (ALT) (P < .001). Among DCH‐positive HPD case 2/9 an 7/9 were acute and chronic hepatitis, of which 4/7 had hepatitis. Log viral copy number (LVCN) was positively correlated with ALT (P < .001), triglyceride (P < .001), and gamma‐glutamyl transpeptidase (GGT) (P = .022). The LVCN also had a positive association with degree of hepatitis (P < .05). There was hepatocyte proliferation activity in DHC positive cats.

Conclusion and Clinical Importance

Domestic cat hepadnavirus infection was associated with high serum activity of liver enzymes and chronic lymphoplasmacytic hepatitis (LPH).

Constrained evolution of overlapping genes in viral host adaptation: Acquisition of glycosylation motifs in hepadnaviral precore/core genes

Hepadnaviruses use extensively overlapping genes to expand their coding capacity, especially the precore/core genes encode the precore and core proteins with mostly identical sequences but distinct functions. The precore protein of the woodchuck hepatitis virus (WHV) is N-glycosylated, in contrast to the precore of the human hepatitis B virus (HBV) that lacks N-glycosylation. To explore the roles of the N-linked glycosylation sites in precore and core functions, we substituted T77 and T92 in the WHV precore/core N-glycosylation motifs (⁷⁵NIT⁷⁷ and ⁹⁰NDT⁹²) with the corresponding HBV residues (E77 and N92) to eliminate the sequons. Conversely, these N-glycosylation sequons were introduced into the HBV precore/core gene by E77T and N92T substitutions. We found that N-glycosylation increased the levels of secreted precore gene products from both HBV and WHV. However, the HBV core (HBc) protein carrying the E77T substitution was defective in supporting virion secretion, and during infection, the HBc E77T and N92T substitutions impaired the formation of the covalently closed circular DNA (cccDNA), the critical viral DNA molecule responsible for establishing and maintaining infection. In cross-species complementation assays, both HBc and WHV core (WHc) proteins supported all steps of intracellular replication of the heterologous virus while WHc, with or without the N-glycosylation sequons, failed to interact with HBV envelope proteins for virion secretion. Interestingly, WHc supported more efficiently intracellular cccDNA amplification than HBc in the context of either HBV or WHV. These findings reveal novel determinants of precore secretion and core functions and illustrate strong constraints during viral host adaptation resulting from their compact genome and extensive use of overlapping genes.

Hepadnaviruses infect a wide range of hosts. The human hepatitis B virus (HBV) and woodchuck hepatitis virus (WHV) are two closely related hepadnaviruses. In contrast to the WHV precore protein, which is N-glycosylated, the HBV precore protein lacks N-glycosylation. As precore and core proteins expressed from the overlapping precore/core genes share most of their sequences but have distinct functions, we investigated the roles of the N-linked glycosylation sequons in HBV and WHV precore/core genes. Our results revealed an important role of the N-linked glycosylation sequons in enhancing precore secretion levels and regulating core protein functions in virion secretion and infection. Furthermore, cross-species complementation assays using HBV and WHV core proteins and HBV or WHV genomes defective in core protein expression indicated that both HBV and WHV core proteins could support intracellular viral replication but not virion secretion of the heterologous virus. These results provide novel insights into the evolution of overlapping genes during host adaptation of hepadnaviruses.

Hepatocellular Carcinoma in a Free-Ranging Three-Toed Sloth (Bradypus variegatus)

The increasing interest of tumors in wildlife is important for biodiversity conservation and for monitoring environmental agents and/or contaminants with potential impact on human health. Here we described the occurrence of hepatocellular carcinoma (HCC) in noncirrhotic liver of a free-ranging three-toed sloth (Bradypus variegatus) from the Atlantic Forest biome in Brazil. The HCC showed a moderate mononuclear inflammatory infiltrate within the tumor tissue but with no inflammation and fibrosis in the adjacent liver tissue. Upon immunohistochemistry, neoplastic cells were diffusely positive for HepPar-1 and glutamine-synthetase presenting an irregular and random immunostaining pattern; β-catenin was positive in the cytoplasmic membrane of malignant hepatocytes; and cytokeratin 19 immunostaining was restricted to bile duct epithelial cells. The liver tissue was negative for HBV-like and HCV-like viruses assessed by molecular tests. The potential similarity of pathogenesis may reinforce the need for research on environmental and/or infectious agents associated with HCC that may contribute to the understanding of cancer in wildlife.

Generalized and fatal felid alphaherpesvirus-1 natural infection with liver involvement in a feline leukaemia virus-positive adult cat: a case report

Generalized and fatal felid alphaherpesvirus-1 (FeHV-1) natural infection with liver involvement is rarely reported in cats, and the occurrence of herpesvirus viraemia with internal organ histologic lesions in adult cats is unknown. A 1.5-year-old cat, female, mixed breed, positive for feline leukaemia virus (FeLV) presented in a veterinary teaching hospital with sneezing, nasal discharge, anorexia, and diarrhoea after two weeks, evolving to inspiratory dyspnoea. Complete blood count and serum biochemistry analysis showed marked leukopenia and thrombocytopenia. After clinical worsening and lack of treatment response, the cat was euthanized. Pathological findings included hepatic necrosis, fibrinonecrotic tracheitis, and bronchointerstitial pneumonia. Marked amounts of coccobacillary bacteria were observed covering the necrotic tracheal and bronchial mucosa, at the cytoplasm of alveolar macrophages, and free in alveoli lumen, mimicking a primary bacterial tracheitis and pneumonia. Both lung and tracheal bacteria exhibited marked immunolabeling in anti-Escherichia coli immunohistochemistry. In addition, rare epithelial cells of bronchi contained round, eosinophilic, intranuclear viral inclusion bodies (4-7 µm) that marginate the chromatin, characteristic of FeHV-1 infection. Strong multifocal anti-FeHV-1 immunolabeling was observed in necrotic epithelial cells of the liver, trachea, and lungs. Generalized herpesvirus infection with the occurrence of acute hepatic necrosis and severe respiratory illness is a potential differential diagnosis in FeLV-positive cats with respiratory signs. The immunodepression in these cats probably favours a FeHV-1 viraemia in addition to the development of opportunistic bacterial infections, such as Escherichia coli, and it is associated with a poor outcome.

Hepadnavirus DNA Is Detected in Canine Blood Samples in Hong Kong but Not in Liver Biopsies of Chronic Hepatitis or Hepatocellular Carcinoma

Chronic hepatitis and hepatocellular carcinoma (HCC) caused by the hepadnavirus hepatitis B virus (HBV) are significant causes of human mortality. A hepatitis-B-like virus infecting cats, domestic cat hepadnavirus (DCH), was reported in 2018. DCH DNA is hepatotropic and detectable in feline blood or serum (3.2 to 12.3%). Detection of HBV DNA has been reported in sera from 10% of free-roaming dogs in Brazil, whereas 6.3% of sera from dogs in Italy tested positive for DCH DNA by real-time quantitative PCR (qPCR). If DCH, HBV, or another hepadnavirus is hepatotropic in dogs, a role for such a virus in the etiology of canine idiopathic chronic hepatitis (CH) or HCC warrants investigation. This study investigated whether DCH DNA could be detected via qPCR in blood from dogs in Hong Kong and also whether liver biopsies from dogs with confirmed idiopathic CH or HCC contained hepadnaviral DNA using two panhepadnavirus conventional PCRs (cPCR) and a DCH-specific cPCR. DCH DNA was amplified from 2 of 501 (0.4%) canine whole-blood DNA samples. A second sample taken 6 or 7 months later from each dog tested negative in DCH qPCR. DNA extracted from 101 liver biopsies from dogs in Hong Kong or the USA, diagnosed by board-certified pathologists as idiopathic CH (n = 47) or HCC (n = 54), tested negative for DCH DNA and also tested negative using panhepadnavirus cPCRs. This study confirms that DCH DNA can be detected in canine blood by qPCR, although at a much lower prevalence than that reported previously. We identified no evidence to support a pathogenic role for a hepadnavirus in canine idiopathic CH or HCC.

Global Prevalence of Domestic Cat Hepadnavirus: An Emerging Threat to Cats’ Health?

Hepatitis B is an infectious hepatocellular disease of global concern caused by hepatitis B virus (HBV), which belongs to Hepadnaviridae. Recently, a novel HBV-like virus, domestic cat hepadnavirus (DCH), was detected from an immunocompromised cat with a hepatic disease in Australia. Subsequent molecular investigation by independent research groups revealed that its prevalence rates were 6.5% in Australia, 10.8% in Italy, 12.4% in Thailand, 12.3% in Malaysia, 3.08% in the United Kingdom, and 0.78% in Japan. Although the correlation between DCH infection and hepatic diseases remains to be elucidated, understanding the diversity of circulating DCH will contribute to its prevention and control in domestic cats. Herein, we summarize the current epidemiological data of DCH in these countries.

Evaluating the presence of domestic cat hepadnavirus viraemia in cats with biochemical alterations suggestive of liver disease

BACKGROUND

The association between domestic cat hepadnavirus (DCH) infection and feline chronic hepatitis and hepatocellular carcinoma has been suggested. However, studies focused on the association between DCH infection and clinicopathological changes consistent with liver disease in cats are not available.

METHODS

This retrospective investigation included sera obtained from 96 cats that had the serum activity of at least alanine aminotransferase or alkaline phosphatase measured during initial diagnostic work-up. Based on these haematobiochemical results, cats were categorised according to their likelihood of having liver disease (absent, low, intermediate or high). DCH DNA was detected using real-time PCR, nested PCR and sequencing.

RESULTS

Overall, potential liver damage was observed in 44 cats, including cats with low (n = 14), intermediate (n = 10) and high (n = 20) likelihood of liver disease. Four cats (4.2%) were DCH-positive, with three positive cats belonging to the liver disease group (two with low and one with intermediate likelihood of liver disease).

CONCLUSIONS

Although the pathogenic potential of DCH in cats still has to be clarified, these results suggest that DCH testing should not be based only on the presence of biochemical changes potentially consistent with liver disease.

Identification of domestic cat hepadnavirus from a cat blood sample in Japan

The hepatitis B virus (Hepadnaviridae) induces chronic hepatitis and hepatic cancer in humans. A novel domestic cat hepadnavirus (DCH) was recently identified in several countries, however, the DCH infection status of cats in Japan is unknown. Therefore, we investigated the DCH infection rate of 139 cat samples collected in Japan. We identified one positive blood sample (0.78%) from a 17-year-old female cat with chronically elevated alanine aminotransferase. Phylogenetic analysis demonstrated that the DCH strain identified in this study is genetically different from strains in other countries. Further investigations are required to elucidate the evolution of DCH and the impact of DCH infection on hepatic diseases in domestic cats.

[Modern views on the role of X gene of the hepatitis B virus (Hepadnaviridae: Orthohepadnavirus: Hepatitis B virus) in the pathogenesis of the infection it causes]

The review presents information on the role of hepatitis B virus (Hepadnaviridae: Orthohepadnavirus: Hepatitis B virus) (HBV) X gene and the protein it encodes (X protein) in the pathogenesis of viral hepatitis B. The evolution of HBV from primordial to the modern version of hepadnaviruses (Hepadnaviridae), is outlined as a process that began about 407 million years ago and continues to the present. The results of scientific works of foreign researchers on the variety of the influence of X protein on the infectious process and its role in the mechanisms of carcinogenesis are summarized. The differences in the effect of the X protein on the course of the disease in patients of different ethnic groups with regard to HBV genotypes are described. The significance of determining the genetic variability of X gene as a fundamental characteristic of the virus that has significance for the assessment of risks of hepatocellular carcinoma (HCC) spread among the population of the Russian Federation is discussed.

A novel hepadnavirus in domestic dogs

Hepadnaviruses have been identified in several animal species. The hepadnavirus prototype, human hepatitis B virus (HBV), is a major public health problem associated with chronic liver diseases and hepatocellular carcinoma. Recently, a novel hepadnavirus, similar to HBV, was identified in domestic cats. Since several pathogens can be shared between cats and dogs, we hypothesized that dogs could also harbor hepadnaviruses and we tested a collection of canine sera with multiple molecular strategies. Overall, hepadnavirus DNA was identified in 6.3% (40/635) of canine serum samples, although the viral load in positive sera was low (geometric mean of 2.70 × 10² genome copies per mL, range min 1.36 × 10²—max 4.03 × 10⁴ genome copies per mL). On genome sequencing, the canine hepadnaviruses revealed high nucleotide identity (about 98%) and similar organization to the domestic cat hepadnavirus. Altered hepatic markers were found in hepadnavirus-positive dogs, although the role of hepadnavirus in canine health remains to be elucidated.

Detection of antibodies against Domestic Cat Hepadnavirus using baculovirus-expressed core protein

A novel orthohepadnavirus (Domestic Cat Hepadnavirus: DCH) similar to human hepatitis B virus has been recently detected in serum and liver samples from domestic cats with chronic hepatitis and hepatocellular carcinoma. Molecular investigations by independent research groups around the world have revealed positivity rates ranging from 6.5% to 12.5% in blood samples and up to 14.0% in liver tissue. In this study, we screened an age-stratified collection of feline sera (n = 256) by using an antibody detection ELISA assay based on the recombinant core antigen of DCH (DCHc). Specific antibodies (DCHc Abs) were detected with a prevalence of 25.0%. The DNA of DCH was detected in 35.9% (23/64) of seropositive cats and only in 1.0% (2/192) of seronegative animals. Based on the serological (IgG and IgM anti-DCHc) and virological status, the possible stages of DCH infection were predicted. This article is protected by copyright. All rights reserved.

Comparison of the prevalence of Domestic Cat Hepadnavirus in a population of cats with uveitis and in a healthy blood donor cat population in the United Kingdom

OBJECTIVE

Domestic Cat Hepadnavirus (DCH) is a novel virus recently identified in the domestic cat. Currently, little is known regarding its clinical significance. The hepadnaviridae family includes the Hepatitis B Virus (HBV). Co-infection of HBV and Hepatitis C in humans increases the risk of uveitis. We aimed to determine whether DCH is present in the United Kingdom (UK) and whether DCH warrants investigation as a potential cause of uveitis in cats.

PROCEDURES

Clinical records from the Royal Veterinary College (RVC) and the Animal Health Trust (AHT) were reviewed for feline cases diagnosed with endogenous uveitis. A healthy control group was identified from cats presented to the RVC as blood donors. DNA was extracted from stored blood samples using commercially available kits. Polymerase chain reaction assays were performed to confirm the presence of feline DNA and to detect the presence of DCH DNA using previously described protocols.

RESULTS

Blood samples were available from 65 cats with endogenous uveitis and 43 healthy control cats. Two blood samples from cats with endogenous uveitis tested positive for the presence of DCH DNA. DCH DNA was not detected in the control group. There was no statistically significant difference between the prevalence of DCH between the groups.

CONCLUSIONS

Domestic Cat Hepadnavirus is present in the UK. This study failed to demonstrate a conclusive link between DCH and uveitis in cats, although further studies to investigate an association with other feline diseases are warranted.

Emerging Hepatotropic Viruses in Cats: A Brief Review

The possible role of viruses in feline liver disease has long remained neglected. However, in 2018, an analogue of human hepatitis B virus was identified in cats. Moreover, antibodies for human hepatitis E have been detected consistently at various prevalence rates in cats. Although the correlation between these viruses and the liver injury in cats must be clarified, hepatotropic viruses might represent an increasing risk for feline and public health.

Hepatocyte ploidy in cats with and without hepatocellular carcinoma

BACKGROUND

Domestic cats rarely develop hepatocellular carcinoma. The reason for the low prevalence is unknown. Reductions in hepatocellular ploidy have been associated with hepatic carcinogenesis. Recent work in mice has shown that livers with more polyploid hepatocytes are protected against the development of hepatocellular carcinoma. Hepatocyte ploidy in the domestic cat has not been evaluated. We hypothesized that ploidy would be reduced in peri-tumoral and neoplastic hepatocytes compared to normal feline hepatocytes. Using integrated fluorescence microscopy, we quantified the spectra of ploidy in hepatocellular carcinoma and healthy control tissue from paraffin embedded tissue sections.

RESULTS

Feline hepatocytes are predominantly mononuclear and the number of nuclei per hepatocyte did not differ significantly between groups. Normal cats have a greater number of tetraploid hepatocytes than cats with hepatocellular carcinoma.

CONCLUSIONS

Total hepatocellular polyploidy in normal cat liver is consistent with values reported in humans, yet cellular ploidy (nuclei per cell) is greater in humans than in cats. Tetraploid cat hepatocytes are predominantly mononuclear.

A longitudinal observational study in two cats naturally-infected with hepadnavirus

Hepatitis B virus (HBV) is a major cause of liver disease in humans including chronic hepatitis and hepatocellular carcinoma. Domestic cat hepadnavirus (DCH), a novel HBV-like hepadnavirus, was identified in domestic cats in 2018. From 6.5 %-10.8 % of pet cats are viremic for DCH and altered serological markers suggestive of liver damage have been identified in 50 % of DCH-infected cats. DCH DNA has been detected in association with characteristic lesions of chronic hepatitis and with hepatocellular carcinoma in cats, suggesting a possible association. In this study longitudinal molecular screening of cats infected with DCH was performed to determine if DCH can cause chronic infections in cats. Upon re-testing of sera from five DCH-positive animals, 2-10 months after the initial diagnosis, three cats tested negative for DCH on two consecutive occasions using quantitative PCR. Two other cats remained DCH-positive, including an 8-month-old female cat re-tested four months after the initial positive result, and a 9-year-old male cat, which tested positive for DCH on six occasions over an 11-month period. The latter had a history of chronic hepatopathy with jaundice, lethargy and elevated serum alanine transaminase levels (ALT). During the period of observation, DCH titers ranged between 1.64 × 10⁵ and 2.09 × 10⁶ DNA copies/mL and ALT was persistently elevated, suggesting chronic infection. DCH DNA was not detected in oral, conjunctival, preputial and rectal swabs from the two animals collected at several time points. Long-term (chronic) infection would be consistent with the relatively high number of viremic cats identified in epidemiological investigations, with the possible association of DCH with chronic hepatic pathologies and with what described with HBV in human patients.

Molecular detection and characterisation of Domestic Cat Hepadnavirus (DCH) from blood and liver tissues of cats in Malaysia

BACKGROUND

A new domestic cat hepadnavirus (DCH, family Hepadnaviridae) was first reported from whole blood samples of domestic cats in Australia in 2018, and from cat serum samples in Italy in 2019. The pathogenesis of DCH is unknown, but it was reported in cats with viraemia (6.5-10.8%), chronic hepatitis (43%) and hepatocellular carcinoma (28%). Recent reports suggest that DCH resembles the human hepatitis B virus (HBV) and its related hepatopathies. This study aims to detect and characterize DCH among domestic cats in Malaysia. A cross-sectional study was performed on 253 cats, of which 87 had paired blood and liver samples, entailing whole-genome sequencing and phylogenetic analysis of DCH from a liver tissue sample.

RESULTS

Among the 253 cats included in this study, 12.3% of the whole blood samples tested positive for DCH. The detection rate was significantly higher in pet cats (16.6%, n = 24/145) compared to shelter cats (6.5%, n = 7/108). Liver tissues showed higher a DCH detection rate (14.9%, n = 13/87) compared to blood; 5 out of these 13 cats tested positive for DCH in their paired liver and blood samples. Serum alanine transaminase (ALT) was elevated (> 95 units/L) in 12 out of the 23 DCH-positive cats (52.2%, p = 0.012). Whole-genome sequence analysis revealed that the Malaysian DCH strain, with a genome size of 3184 bp, had 98.3% and 97.5% nucleotide identities to the Australian and Italian strains, respectively. The phylogenetic analysis demonstrated that the Malaysian DCH genome was clustered closely to the Australian strain, suggesting that they belong to the same geographically-determined genetic pool (Australasia).

CONCLUSIONS

This study provided insights into a Malaysian DCH strain that was detected from a liver tissue. Interestingly, pet cats or cats with elevated ALT were significantly more likely to be DCH positive. Cats with positive DCH detection from liver tissues may not necessarily have viraemia. The impact of this virus on inducing liver diseases in felines warrants further investigation.

Seroprevalence of canine hepatitis in stray dogs in Nineveh Province, Iraq

Aim:

The current study was conducted to explore evidence of hepatitis B virus (HBV) infection in dogs in Nineveh Province, Iraq.

Materials and Methods:

Serum samples of 78 dogs were used to (i) estimate levels of the antibodies against HBV through enzyme-linked immunosorbent assay and (ii) measure the activity of liver function enzymes.

Results:

Seropositive dogs for HBV constituted 9% of total tested dogs. The differences in seropositivity among males compared to females and among different ages were not statistically significant. Liver function enzymes analysis revealed a significant increase in the activity of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase in seropositive dogs compared to those seronegative.

Conclusion:

Hepatitis B is evident in dogs in Nineveh Province, Iraq, with a significant impact on liver function in affected dogs. It is important to confirm this evidence through molecular tests.

Insights into the genetic diversity, recombination, and systemic infections with evidence of intracellular maturation of hepadnavirus in cats

Hepatitis B virus (HBV) is a human pathogen of global concern, while a high diversity of viruses related to HBV have been discovered in other animals during the last decade. Recently, the novel mammalian hepadnavirus, tentatively named domestic cat hepadnavirus (DCH), was detected in an immunocompromised cat. Herein, a collection of 209 cat sera and 15 hepato-diseased cats were screened for DCH using PCR, resulting in 12.4% and 20% positivity in the tested sera and necropsied cats, respectively. Among the DCH-positive sera, a significantly high level of co-detection with retroviral infection was found, with the highest proportion being co-detection with feline immunodeficiency virus (FIV). Full-length genome characterization of DCH revealed the genetic diversity between the nine Thai DCH sequences obtained, and that they phylogenetically formed three distinct monophyletic clades. A putative DCH recombinant strain was found, suggesting a possible role of recombination in DCH evolution. Additionally, quantitative PCR was used to determine the viral copy number in various organs of the DCH-moribund cats, while the pathological findings were compared to the viral localization in hepatocytes, adjacent to areas of hepatic fibrosis, by immunohistochemical (IHC) and western blot analysis. In addition to the liver, positive-DCH immunoreactivity was found in various other organs, including kidneys, lung, heart, intestine, brain, and lymph nodes, providing evidence of systemic infection. Ultrastructure of infected cells revealed electron-dense particles in the nucleus and cytoplasm of hepatocytes, bronchial epithelial cells, and fibroblasts. We propose the intracellular development mechanism of this virus. Although the definitive roles of pathogenicity of DCH remains undetermined, a contributory role of the virus associated with systemic diseases is possible.